水热法制备高度取向的氧化锌纳米棒阵列

氧化锌的激子结合能(60meV)及光增益系数(300cm^-1)比GaN的(25meV,100cm^-1)还高,这一特点使它成为紫外半导体激光发射材料的研究热点。最近,Yang等成功地观测到规则的ZnO纳米线阵列的激光发射现象,更加激起了人们合成一维高度有序ZnO纳米结构的热情,由于一维ZnO     

利用水热法制备氧化锌微米球

利用水热法制备出具有特殊形貌的ZnO微米球.利用X射线粉末衍射仪(XRD)和扫描电镜(SEM)对ZnO进行了表征.     

水热合成掺Fe氧化锌复合材料及其光催化活性

以Zn(Ac)2•2H2O、Fe(NO3)3•9H2O和NaOH为原料,采用水热法合成了Fe掺杂ZnO复合材料。并用x射线衍射和扫描电子显微镜技术对合成样品的结构和形貌进行了表征,Fe掺杂ZnO合成产物为直棒状,直径为500 nm,长度为3 µm左右。样品的紫外可见漫反射分析,在300~500 nm紫外可见光区域均有强的吸收。利用Fe掺杂ZnO作为光催化剂降解有机染料,发现对于光催化降解有机染料有较好的降解功能,且光降解性能优于纯ZnO材料。     

Hydrothermal synthesis and their catalytic properties of manganite nanowires

La_0.5Sr_0.5MnO₃ nanowires and nanoparticles were synthesized by the hydrothermal and citrate methods, respectively. The samples were characterized by TEM, HRTEM, XRD, ICP and N₂ adsorption, etc. The formation mechanism of the nanowires was proposed and discussed. Further, the stabilities and catalytic activities of La_0.5Sr_0.5MnO₃ nanowires for CH₄ combustion were evaluated and compared with those of the nanoparticles. The results showed that the particle morphology had a significant effect on the properties of the catalysts. After running at a high temperature for a long duration, the nanowires showed a higher stability and a higher activity, compared with the nanoparticles. Their different stabilities were ascribed to the different surface energies (particle sizes), as well as to the different geometric packing models.     

水热法制备ZnO二维周期有序孔结构薄膜

在由溶胶-凝胶法制备的纳米ZnO薄膜衬底上,以Zn(NO3)2.6H2O和六亚甲基四胺(HMT)等摩尔浓度配制成前驱体溶液,在单层聚苯乙烯(PS)微球模板辅助下,采用水热法制备了具有规则多孔结构的ZnO薄膜。探讨了PS微球作为模板对ZnO纳米棒生长的限制作用以及柠檬酸钠在水热制备方法中对晶体生长的影响。利用扫描电子显微镜(SEM)和X射线衍射(XRD)表征了水热反应后所得二维有序ZnO膜表面形貌和取向性,测量了ZnO薄膜的光致发光(PL)光谱并研究其相应机理。     

Co掺杂ZnO纳米棒的水热法制备及其光致发光性能

以Zn(NO3)2·6H2O 和Co(NO3)2·6H2O为原料, 通过水热法在较低温度下制备了纯ZnO和Co掺杂的ZnO(ZnO:Co)纳米棒. 利用XRD、EDS、TEM和HRTEM对样品进行了表征, 结合光致发光(PL)谱研究了样品的PL性能. 结果表明, 水热法制备纯ZnO和ZnO:Co纳米棒均具有较好的结晶度. Co2+是以替代的形式进入ZnO晶格, 掺入量为2%(原子分数)左右. 纯的ZnO纳米棒平均直径约为20 nm, 平均长度约为180 nm; 掺杂样品的平均直径值约为15 nm, 平均长度约为200 nm左右; Co掺杂轻微地影响ZnO纳米棒的生长. 另外, Co掺杂能够调整ZnO纳米棒的能带结构、提高表面态含量, 进而使得ZnO:Co纳米棒的紫外发光峰位红移, 可见光发光能力增强.     

Hydrothermal oxidation synthesis of rod‐like ZnO and the influence of oxygen vacancy on photocatalysis

Rod‐like ZnO nanoparticles (NPs ) were synthesized from zinc powder by a simple hydrothermal oxidation method. The presence of acetylacetone could promote the oxidation reaction of Zn and the formation of hexagonal nanorods. Then, the as‐prepared samples were annealed in N₂ , O₂ , and air atmosphere at 550°C for 2 h to control the number of oxygen vacancies in the samples. The samples were characterized by X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy, and UV –vis spectroscopy. The correlation between the oxygen vacancies and the photocatalytic activity was investigated. The results reveal that the annealing process alters the samples’ bandgap and number of the oxygen vacancies, thereby improving the photocatalytic activity. The enhancement of photodegradation efficiency arising from the appropriate content of oxygen vacancies is discussed.     

Facile synthesis and photoelectrochemical performance of the bush-like ZnO nanosheets film

Bush-like ZnO nanosheets film is fabricated on conductive transparent oxide substrates using a facile hydrothermal method without any surfactant or further heat treatment. The morphology, structure and photoluminescence property of the products are characterized in detail. The ZnO nanosheets are composed of numerous grains with the 5 nm average diameter, and most of the sheets present the relative uniform arrangement. These nanosheets construct a porous network which is favorable for the photoelectrochemical properties and applications in dye-sensitized solar cells. The photoelectrochemical performances of the bush-like ZnO nanosheets film are investigated, and a high open-circuit voltage of 0.69 V is achieved.     

Hydrothermal synthesis and characterization of hexagonal and monoclinic neodymium orthophosphate single-crystal nanowires

Hexagonal and monoclinic NdPO₄ nanowires about 5-50 nm in diameter and up to several micrometers long were prepared through hydrothermal reaction in 100°C and 220°C, respectively. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS), and high-resolution transmission electron microscopy (HRTEM). Furthermore, both the temperature and the pH value influence on the products were investigated.     

Structural and optical properties of ZnMgO nanostructures formed by Mg in-diffused ZnO nanowires

ZnMgO nanostructures with wurtzite phase were prepared by thermal diffusion of Mg into the ZnO nanowires. As ZnO light-emitting devices have been operated by using ZnMgO layers as energy barrier layers to confine the carriers, it is essential to realize the characterization of ZnMgO particularly. In this work, the Mg content in Zn_1−xMg_xO alloy determined by X-ray diffraction (XRD) and photoluminescence (PL) shows a good coincidence. The variation of lattice constant and the blueshift of near-band-edge emission indicate that Zn²⁺ ions are successfully substituted by Mg²⁺ ions in the ZnO lattice. In Raman-scattering studies, the change of E₂(high) phonon line shape in ZnO:Mg nanostructures reveals the microscopic substitutional disorder. In addition to the host phonons of ZnO, two additional bands around 383 and 510 cm⁻¹ are presumably attributed to the Mg-related vibrational modes.     

Dark Color ZnO Quasi-One-Dimensional Nanostructures Grown by Hydrothermal Method and Modulation of their Optical Properties

Zinc oxide has a large energy gap and thus it has potential application in the field of solar cells by tuning the absorption of sunlight. In order to enhance its absorption of sunlight, dark color zinc oxides have been prepared by traditional hydrothermal method directly using a zinc foil as both source and substrate. We found that we could tune the optical properties of ZnO samples by changing the temperature. In particular, increasing temperature could significantly reduce the reflectivity of solar energy in the visible range. We speculate that the phenomenon is relevant to the sharp cone morphology of the ZnO nanorods grown on the surface of Zn foils, which furthermore enhance refraction and reflection of light in the nanorods. The capacity to improve the light absorption of ZnO may have a bright application in raising the efficiency of solar cells.     

Hydrothermal synthesis of 2D ordered macroporous ZnO films

The ZnO films with two-dimensional ordered macroporous structure were successfully fabricated through hydrothermal crystal growth of ZnO on the ZnO substrate covered with a monolayer of polystyrene (PS) spheres as template. The precursor solution of hydrothermal crystal growth of ZnO were prepared by equimolar solution of Zn(NO₃)₂·6H₂O and hexamethylenetramine (HMT). The confinement effect of the PS spheres template on the growth of ZnO nanorods and the influence of sodium citrate on the crystal growth of ZnO had been studied. The film surface morphology and the preferential growth of ZnO crystal were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Also, the photoluminescence spectrum of ZnO films had been measured, and the corresponding mechanism was discussed. __________ Translated from Chemistry, 2007, 70 (8): 587–592 [译自: 化学通报]     

Rapid Synthesis and Photoluminescence Properties of Eu-doped ZnO Nanoneedles via Facile Hydrothermal Method

Eu-doped ZnO nanoneedles with different doping concentrations were prepared via the facile hydrothermal method.The crystal structure,morphology and photoluminescence property of the ZnO nanoneedles were characterized by X-ray diffraction（XRD）,scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）,photoluminescence spectroscopy（PL） and Raman spectroscopy.The results show that the europium ions are incorporated into the crystal lattice of ZnO matrix in trivalent ions.The nanoneedles are 2-3 μm in length and 100 nm in the tip diameter.PL and Raman measurements indicate that higher Eu^3＋ doping concentration may destroy the crystallization of the nanoneedles and decrease the ratio of IUV/IDLE,which is mainly due to the more defects in the doped ZnO nanoneedles.And the characteristic red emissions of Eu^3＋ ions are found by the PL spectroscopy with the Eu^3＋doping concentration increasing,which are attributed to the ^5D0→^7F0,^5D0→^7F1 and ^5D0→^7F2 transitions.     

Hydrothermal Growth of Ag‐Doped ZnO Nanoparticles on Electrospun Cellulose Nanofibrous Mats for Catechol Detection

We fabricated a novel hierarchical composite mat composed of electrospun cellulose nanofibers decorated with Ag‐doped ZnO (Ag‐ZnO) nanoparticles and further demonstrated its potential application as the efficient laccase (Lac) biosensor substrate material. The cyclic voltammograms revealed that the Ag‐ZnO/cellulose nanofibrous mat provided an excellent microenvironment for Lac immobilization and benefited direct electron transfer of Lac. The fabricated Lac/Ag‐ZnO/cellulose/GCE exhibited a highly sensitive detection of catechol with a wide linear range from 0.995 to 811 µM and a low detection limit of 0.205 µM. The results indicated that Ag‐ZnO/cellulose nanofibers were the promising nanostructured materials for the construction of different biosensors.     

PEG辅助氧化锌纳米棒的水热法制备

采用PEG辅助水热法合成了ZnO纳米棒,XRD显示产物为结晶良好的六角结构晶体ZnO,PL谱表明适当退火处理后产物有较好的光致发光性能.利用TEM和SAED研究了纳米棒的形貌和生长机制,并研究了氢氧化钠浓度和反应时间对产物形态和尺寸的影响.     

合成ZnO纳米阵列及刺突状CuO/ZnO异质结

采用低温水热法在掺氟SnO₂ (FTO)导电玻璃表面制备ZnO纳米阵列, 研究了前驱体溶液浓度摩尔配比对ZnO纳米阵列形貌、光学性能及其生长机理的影响. 研究发现, 随着前驱体溶液浓度摩尔配比的增加, ZnO纳米阵列形貌及光学性能也随之变化. ZnO纳米阵列高度逐渐降低, ZnO纳米阵列直径和光学带隙值大体上出现先增大后降低的趋势. 而当前驱体溶液(Zn(NO₃)₂:环六亚甲基四胺(HMT, C₆H₁₂N₄))浓度摩尔配比为5:5时, 其光学禁带值(3.2 eV)接近于理论值. 结果显示制备ZnO纳米阵列的最优浓度摩尔配比为5:5. 随后选用最优浓度摩尔配比下制备的ZnO纳米阵列为基底, 通过一种两步溶液法成功在其表面制备刺突状CuO/ZnO异质结.从场发射扫描电镜(FE-SEM)结果中可以清楚看见, 大量的CuO纳米粒子沉积在ZnO纳米阵列表面形成刺突状异质结结构.研究发现该CuO/ZnO纳米异质结相对于纯ZnO纳米阵列在紫外光下光催化性能明显增加. 最后, 讨论了CuO/ZnO纳米异质结光催化机理.     

双盘状ZnO的可控制备

采用水热法制备了形貌可控、 尺寸均一的双盘状ZnO. X射线粉末衍射(XRD)、 扫描电子显微镜(SEM)及透射电子显微镜(TEM)等测试结果表明, 制备的ZnO具有六方纤锌矿结构, 由2个直径约为4 μm, 厚度约为600 nm的圆盘复合而成. 考察了反应温度和乙酸锌与柠檬酸钾的摩尔比对产物形貌与尺寸的影响, 实现了双盘状ZnO的可控合成, 并初步探讨了其形成机理. 荧光光谱显示, 双盘状ZnO的紫外发射峰半高宽约为10 nm, 比块体ZnO的紫外发射峰半高宽(18 nm)窄, 表明双盘状ZnO具有更好的光学特性.     

纳米ZnO的制备及其光学性质的研究

采用均匀沉淀法，以尿素与硝酸锌反应制备纳米ZnO，通过TG-DTA、XRD、IR及TEM等手段对纳米粒子及中间体进行了表征，结果表明制得的纳米粒子粒度均匀，粒径分布窄。对纳米ZnO的发光特性研究表明，随焙烧温度升高，粒度的增大，可见绿色发射增强。同时对纳米ZnO与普通ZnO的发光性质进行了比较研究，指出纳米ZnO的绿色发光带有蓝移现象，这是由于纳米ZnO的量子尺寸效应引起的。BET测试表明，纳米ZnO的比表面为171．2m^2／g，有利于作催化剂。     

Hydrothermal synthesis and thermodynamic analysis of dawsonite-type compounds

Dawsonite-type compounds of formula MAl(OH)₂CO₃ (M=Na,K,NH₄) were hydrothermally synthesized. The influences of the composition of starting materials, reaction temperature, acidity of the reaction medium on the formation, morphology and particle size of MAl(OH)₂CO₃ powders were systematically investigated. The experiment results show that increase in the amount of MHCO₃ favors the formation of MAl(OH)₂CO₃ phase with more slender particle morphology. The higher the reaction temperature, the grosser the particle is. It was also demonstrated that the particle size of the MAl(OH)₂CO₃ phase are most uniform when the pH value of reaction system is 10.3 for sodium dawsonite and potassium dawsonite, but it is 9.79 for that of ammonium dawsonite. The thermodynamics of the formation of dawsonite-type compounds have also been analyzed in details.     

酸碱度调控氧化锌纳米材料形貌及其光催化还原CO2研究

利用水热法合成了形貌可控的氧化锌(ZnO)微纳材料。利用X射线衍射(XRD),扫描电子显微镜(SEM),透射电子显微镜(TEM),紫外-可见(UV-Vis)分光光谱和比表面积分析(BET)等技术对所制备的ZnO材料进行了表征。不同酸碱度(pH值)条件下,经过500 ℃退火2 h制备的ZnO均为纤锌矿结构。随着前驱液pH值的增加,所得ZnO从片状晶体变为棒状晶体。片状ZnO主要暴露极性晶面,棒状ZnO主要暴露非极性晶面。从生长角度考虑,在溶液为弱酸性条件下(pH 6.5),溶液中游离的氯离子(Cl^-)抑制了ZnO在锌极性面({Zn²⁺}_{crystal surface})的生长,水热反应产物为片状Zn₅(OH)₈Cl₂·H₂O,退火后得到微孔片状ZnO;当溶液中添加氢氧根(OH^-)后,锌离子(Zn²⁺)被络合为四羟基锌络合离子(Zn(OH)₄^2-),该络离子促进了ZnO在{Zn²⁺}_{crystal surface}的生长,从而得到棒状晶体。利用上述催化剂,在氙灯照射下进行光催化还原二氧化碳实验,发现极性面较多的片状ZnO具有更高的光催化性能。